""Live long...and prosper, Spock."
This isn't as generic as it sounds, as the addition of Spock's name at the end is kind of unique to a particular scene. I have a strong feeling it's the final line said to him by the Vulcan high priestess (can't remember her name) at the beginning of The Motion Picture.
Anyway, since I got one of my own, here's one:
"You are mad..."